Known mail sorting systems such as DBCS and MLOCR machines include a feeder that feeds mail pieces one at a time to a pinch belt conveyor that transports singulated mail pieces during the sorting process. In one common version of such a system, a pickoff belt mechanism is positioned to frictionally engage an outer surface of a mail piece at the end of a stack and transport it transversely to a thickness direction of the stack, which pickoff mechanism includes one or more belts mounted on rollers and driven by a drive motor; a sensor positioned to determine mail piece movement speed as the mail piece is being transported by the pickoff belt mechanism; a measurement device for determining belt movement speed during operation of the pickoff belt mechanism a vacuum pump; a vacuum manifold connected to the vacuum pump, wherein the vacuum manifold is positioned to apply suction to the mail piece in a direction that tends to hold the mail piece against the belt of the pickoff belt mechanism; optionally means for stopping slipping of the mail piece relative to the belt during transport by the belt pickoff mechanism may also be provided, such as by temporarily increasing suction force applied to a mail piece being transported by the pickoff belt mechanism. Two known pickoff mechanisms are shown in U.S. Patent publications 20100034623 PICKOFF MECHANISM FOR MAIL FEEDER and 20100032889 PICKOFF MECHANISM FOR MAIL FEEDER.
A stripper is commonly provided at a position a short distance upstream from the pickoff belts. A problem arises when the pickoff belts remove two mail pieces at the same time from the stack. When such a double feed happens, a stripper is positioned a short distance upstream. See, e.g., U.S. patent publication 20090206014 to Enenkel at stripper 56. The stripper generally takes the form of a metal plate or block, that is, a friction shoe that is positioned to contact and pull off a second mail piece resting side by side with the first fed through. The second mail piece is later carried on into the pinch belt transport belts after the first one has been carried on.
The stripper plays a key role in singulation of mail on feeders. However, slow response time and improper damping of existing strippers leads to frequent doubles. The location of the friction surface is governed by the location of brackets and a bar mechanism onto which the friction shoes are mounted. The friction shoes wear over time and therefore the location of the friction surface has to be adjusted by adjusting the location of mounting brackets. Contrary to the desired dragging mode of force application on the mail pieces, known strippers apply a normal (perpendicular) load on the mail piece. In one known stripper the links used for shoe mounting are rigid hence a large point force acts on the mail and the mail is constrained at single point. The mail pieces being fed therefore can flap, bend and become damaged. The normal spring forces lead to head-on impact of the mail with the friction shoe. Large impact and corresponding displacement of the friction shoes causes lots of noise. Little attention has been paid in the art to the fabrication of the stripper and means of improving its performance. The present invention addresses these issues.